Edelbrock 650 Thunder Series Carb... Issues! HELP!

Not an expert with the Thunder series, but generally a WOT stumble is a lean condition.

This can be caused by

1 - a sloppy air valve as 70aar stated , or

2 - Just too plain lean in the jetting (too much air, not enough fuel when it opens)

Put the air valve back close to factory spec if it didn't change it much - and concentrate on jetting.

I'd be copying the AFB jetting to start with - especially the primary side....that way you know you're in the ball park.

FWIW - If that 360 is running a mild cam - at a hunch Id be running .110 primaries and .104 secondaries as a start point...with rods around 73x.42 or whatever is close in "thunder speak".